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How To: Add Multicore vCPUs in vSphere 4.1

With the release of VMware vSphere 5, VMware added GUI capabilities which allows you to tweak how many virtual CPUs and how many cores per virtual CPU each VM was configured with. This is a very useful tool because many times you come across operating systems and even applications that are limited in terms of the number of CPU sockets that they support, conversely, having the ability to add cores per virtual CPU socket increase performance quite a bit. This is a cool new GUI addition, but the technology exists in vSphere 4.1 as well, albeit not very apparent and requires manual configuration.

Now before I go any further and delve into how to configure this in vSphere 4.1, it is worth noting that this technology was ported from VMware Workstation, it existed in VMware Workstation for many versions now, VMware tends to release features and functionality into the Type-2 hypervisors first as a way of vetting its stability and functionality before it is released in the enterprise products, not a bad approach at all.

For those of you that want to configure virtual machines with multiple vCPUs and multiple cores per vCPU on vSphere 4.1, follow these steps:

  1. Right-click a VM and click on Edit Settings
  2. Click on the Options tab
  3. Choose General in the Advanced Options list
  4. Click Configuration Parameters
  5. Click Add Row
  6. Add cpiid.coresPerSocket in the name column
  7. Enter the number of cores you want in the value column, a value of 2, 4 or 8 is valid, of course the 8 cores, Enterprise Plus licensing required for the latter.
  8. Click OK and Power On your VM

It is worth noting here that when using this feature, the CPU Hot Add / Remove is disabled. This is a really cool feature and ofr those that are not ready to go to vSphere 5 just yet, I wanted to make sure that you were aware of it.

Posted by Elias Khnaser on 12/20/2011 at 12:49 PM


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